It’s a great word, isn’t it? Bibliomancy
It means to “consult” seemingly random passages from books as messages or guides–or in this case starting points or prompts.
(Officially it means: “foretelling the future by interpreting a randomly chosen passage from a book, especially the Bible.” From Wikipedia: “Bibliomancy is the use of books in divination.”)
Open the closest book and put your finger down on the page. Where it “lands” is your story starter: Use that sentence as a first line (or maybe the title)…
(Here is my result, from On Earth We Are Briefly Gorgeous: “What’s left of November seeps through their jeans, their thin knit sweaters.”)